Conventionally, the rear body structure of a vehicle includes a series of structures, located at the rear of the fuel tank, which are intended to absorb impact energy by deforming in response to an impact at the rear of the vehicle, and thus protect the fuel tank in the case of such an impact. These structures include a rear bumper beam and crash boxes, located between the rear ends of the rear rails of the rear body structure and the bumper beam.
The rear rails are located in front of the crash boxes. They conventionally have a resistance that is greater than that of the bumper beam and of the crash boxes and are intended for transferring the impact forces to the structural elements of the vehicle body. A front portion of the rear rails extends alongside the fuel tank of the vehicle, which is usually located at the rear end of the vehicle, in front of the wheel casings.
It appears that, in the case of high speed impacts on the rear of the vehicle, the conventional shock absorbing structures mentioned above may not sufficiently absorb the impact energy and the impact may result in a crushing of the rear rail(s). Such an uncontrolled crushing may result in an intrusion of some elements of the rear body structure into the gas tank, thus causing damage to the fuel tank, which might lead to spilling of the fuel and may ultimately result in an explosion of the vehicle. Therefore, damage to the fuel tank should be avoided, even in the case of high speed impacts.